THE OPEN-HEARTH FURNACE. . 125
ganese, carbon and iron are absorbing oxygen from the gases. A carbonic oxide flame can be made, more nearly neutral than any other, and hence is. more desirable at the end of the operation.
SEC. VIIIc.—Construction of a furnace.—In the furnace exhibited in Fig. VIII-A the hearth sits partly upon the arches of the chambers. These arches, during the entire run of the furnace, are at a bright yellow heat and are subjected to strains and deformation by the alternating shrinking and expansion of the walls that support them. A poorer foundation for a furnace would be difficult to conceive, and some day there must be a long stop to make what are called "general repairs," this term being often used to cover the alterations consequent upon defective installation.
It is not easy to say just what the best construction is to avoid these difficulties. H. W. Lash, of Pittsburg, devised horizontal chambers, and thereby the charging floor of the furnace was brought down to the general level, and it was.not necessary to elevate the stock. There are objections, however, to horizontal chambers, for the tendency of the hot gases is to seek the upper passages and the benefit of the full area is not secured. In vertical chambers, on the contrary, there is an automatic regulation of the current; for, if there is a hot place, the in-going cool gases naturally seek it, and if there is a cool place, the out-going hot gases find it, and there is a constant tendency to equalization and to the highest efficiency of a given regenerator content. The worst feature of horizontal chambers is the lack of-any propelling action of the gases. With vertical regenerators the hot gas and air rise naturally and force themselves into the furnace, but with horizontal passages there is only a slight positive pressure due to the short up-take near the furnace. The fuel will and should leave the producer under a slight pressure, so that it will need no further assistance on its way to the furnace, but it is advisable to force the air with a fan-blower.
The room necessary in a regenerator is something on which there is. great difference of opinion, but a much larger amount is economical than is generally given. If the chambers are large enough, all the heat can be intercepted, and the gases will go to the stack at the temperature of the incoming gas and the incoming air, but this would be carrying things to an extreme. The gases should not be at a red heat, although a very large number of furnaces are running with fair fuel economy where the gases, during